Near-Earth Asteroid 2015 TB145 Passes By Without a Fright!

Scientists from the Planetary Radar Group at the Arecibo Observatory, a facility of the National Science Foundation (NSF), observed near-Earth asteroid 2015 TB145 on the eve of Halloween, October 30, 2015. The NASA-funded planetary radar system measured 2015 TB145 to be about 600 meters (2,000 feet) in diameter, which is much larger than expected, with a rotation period of approximately 5 hours and velocity of 35 km per second.

This asteroid, discovered on October 10, will make its closest approach to Earth on the morning of Halloween, October 31, 2015, when it is 1.3 times farther away from Earth than the Moon. Observers with small telescopes may catch a glimpse of asteroid 2015 TB145 near the constellation Ursa Major.

Observations of this asteroid were also conducted jointly with other radio telescopes across the United States, including NASA Jet Propulsion Laboratory's Goldstone solar system Radar and National Radio Astronomy Observatory's Green Bank Telescope and Very Long Baseline Array. Data from these observations will be used to determine the asteroid's shape, rotation, and surface properties as well as allow for refinement of the asteroid's orbit, which can be used to better assess its impact hazard. The Arecibo Observatory will also observe this asteroid on Halloween Day.

Asteroid 2015 TB145 was recently discovered by the Pan-STARRS I survey in Hawaii and classified as a potentially hazardous asteroid due to its size and relative proximity to Earth. "One of the directives of the Arecibo Observatory is to measure with high precision the distance to asteroids and their speed, which can be used to study the asteroid's orbit and predict its motion for hundreds of years," said Dr. Edgard Rivera-Valentin, a Universities Space Research Association (USRA) Planetary Scientist at the Arecibo Observatory. Tracking of 2015 TB145 has shown that it is not a threat and will not have a similarly close approach to Earth during this century.

"Our measurements also allow for high-resolution images surpassed only by dedicated space missions sent to asteroids. The difference is our work is much more cost efficient and can survey many times more asteroids," added Dr. Patrick Taylor, USRA Group Lead for the Planetary Radar Group.

Radar images obtained at the Arecibo Observatory appear to rotate clockwise, which is noticeable by the movement of bright features. "The bright and dark features are indication of surface irregularities. For example, the central dark feature may be a large circular depression, possibly an impact crater," commented Dr. James Richardson, USRA Scientist in the Planetary Radar Group.

The Arecibo Observatory has observed over 80 asteroids so far this year and will continue to monitor the skies to improve our understanding of the impact hazard objects such as Asteroid 2015 TB145 pose to Earth.

Image and animation:Arecibo radar images of asteroid 2015 TB145 with resolution of 7.5 meters (25 feet). The frames are snapshots throughout the 40-minute-long observation. Bright features on the surface appear to rotate clockwise from image to image. The darker features may be depressions on the surface.

Located in Puerto Rico, the Arecibo Observatory is home to the largest and most sensitive single dish radio telescope in the world. The Arecibo Observatory is operated by SRI International in partnership with Ana G. Méndez University System-Universidad Metropolitana and Universities Space Research Association (USRA) under a cooperative agreement with the NSF. The Arecibo Planetary Radar program is supported by NASA's Near Earth Object Observation program.